Meet the Amazing SSH

Category: Miscellaneous

If you access remote computers via a command line interface meet the amazing ssh (Secure SHell). At the most basic level ssh is the modern day equivalent of telnet, but, it is also much more. Even if you don't need the advanced features of ssh you should be using it rather than telnet because ssh will encrypt your password before sending it over the Internet, telnet does not. You read right, telnet sends your password in clear text across the network. But, that isn't what got me to writing this evening, the really cool thing about ssh is that you can use it to forward ports over a secure connection. For example, say your on a network that doesn't allow sending mail to port 25, but, you can ssh to a server you can send mail from, you can use ssh to forward a local port to port 25 on the remove server. Or, say you are accessing a remote machine, but, want to connect to a service that is on your local machine behind a firewall, ssh to the rescue again, just tell ssh to forward a remote port back to your local machine.

In my case I use this technique to allow a Perforce client on my remote webserver to connect the the Perforce server on my laptop. I run the Perforce server on the loop back interface because I know that IP address will never change regardless of what network my laptop is connected to, then, I ssh to the remove server with the following command.

ssh <username>@<servername> -R 2200:127.0.0.1:2200

Using this command I can use the p4 client at "servername" to connect to the perforce server at 127.0.0.1:2200 on my local machine.

Don't forget ssh's cousin sftp and if you want to get a look at all that network traffic Wire Shark (formally Ethereal).

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